Index: django/contrib/admin/sites.py
===================================================================
--- django/contrib/admin/sites.py	(revision 7396)
+++ django/contrib/admin/sites.py	(working copy)
@@ -228,6 +228,8 @@
                     user = User.objects.get(email=username)
                 except User.DoesNotExist:
                     message = _("Usernames cannot contain the '@' character.")
+                except User.MultipleObjectsReturned:
+                    message = _("Your e-mail address is not your username")
                 else:
                     message = _("Your e-mail address is not your username. Try '%s' instead.") % user.username
             return _display_login_form(request, message)